Radial piston pump

ABSTRACT

The invention relates to a multistage radial piston pump assembly. The assembly has two or more spaced-apart piston carriers attached to a shaft, the piston carriers having radially disposed cylinders with pistons disposed therein. A pivotally adjustable track carrier surrounds each piston carrier. Casing parts between each adjacent pair of piston carriers each has passages in fluid communication with the inlet and outlet ports of the assembly. At least one of these casing parts has the passages thereof in fluid communication with each of the piston carriers on opposite sides thereof through the sidewalls of the casing part. Regulatory means are provided for a three-stage assembly so that the eccentricity of the track carrier surrounding the middle piston carrier is always in the opposite direction of the eccentricities of the other two track carriers relative to the other two corresponding piston carriers.

United States Patent [72] Inventor Carl V. Ohrberg Nordborg, Denmark [21] Appl. No. 3,084 [22] Filed Jan. 15, 1970 [45] Patented Oct. 19, 1971 [73] Assignee Danfoss A/S Nordborg, Denmark [32] Priority Feb. 17,1969 [33] Germany [31] P 19 07 840.1

[54] RADIAL PISTON PUMP [50] Field of Search e 238; 91/492, 497

[5 6] References Cited UNITED STATES PATENTS 2,328,717 9/1943 Glasner 91/497 X Primary Examiner-Robert M. Walker Att0rney--Wayne B. Easton ABSTRACT: The invention relates to a multistage radial piston pump assembly. The assembly has two or more spacedapart piston carriers attached to a shaft, the piston carriers having radially disposed cylinders with pistons disposed therein. A pivotally adjustable track carrier surrounds each piston carrier. Casing parts between each adjacent pair of piston carriers each has passages in fluid communication with the inlet and outlet ports of the assembly. At least one of these casing parts has the passages thereof in fluid communication with each of the piston carriers on opposite sides thereof through the sidewalls of the casing part. Regulatory means are provided for a three-stage assembly so that the eccentricity of the track carrier surrounding the middle piston carrier is always in the opposite direction of the eccentricities of the other two track carriers relative to the other two corresponding piston carriers.

PATENTEBUET 19 ten SHEEI E OF 6 PATENTEDum 19 Ian SHEEI 30F 6 Zic RADIAL PISTON PUMP The invention relates to a radial piston pump comprising a driving shaft and two parts rotatable relatively to each other, one of which, a piston carrier, has radially disposed cylinders for accommodating the pistons as well as distributing passages extending from each of the inner ends of the cylinders to a transfer surface, and the other, a track carrier, carries a curved path for guiding the outer ends of the pistons. The idea covered is that of the piston carrier being held by at least one end-face against a wall of the track carrier and the transfer surface being formed on this end-face.

In this arrangement the piston carrier can be secured directly on the driving shaft which passes through it. The pressure and suction passages do not extend through the shaft but through the casing. Despite a small diameter of shaft and small pump dimensions, flow orifices of sufficient size are obtained on the transfer surface. The losses by leakage can be kept very low.

In particular the present invention relates to a construction in which the piston carriers of at least two pump units are fitted on a common shaft containing no pressure and suction passages.

Whereas in the known radial piston pumps, the shaft had to be connected, through a coupling, with a journal in which suction and pressure passages were formed, in accordance with the inventionany required number of pump units can be fitted on a single straight-through shaft. The number of pump units depends solely upon the power required and available. These pump units can be independent of each other apart from their common drive, and they can each provide their own hydraulic system. The pump units can however also act on a single system either by being arranged in series in the form of a multistage pump to provide high pressure, or by being arranged in series in parallel with each other for a pump of higher capacity. Greatly differing combination are also possible. The pump units can be of different size. It is even possible to use the same driving shaft for also powering a pump unit of another type, e.g. a rotary piston pump.

A further simplification is achieved in that, on the two sidewall surfaces of a casing part disposed between the piston carriers of neighboring pump units, said part contains the mouthsof passages cooperating with transfer surfaces of both pump units. In this arrangement it is particularly advantageous if these casing parts contain at least one passage common to both pump units. The common passage can, for example, form the suction passage of two pump units, whether these be arranged in parallel or operate separately. In the case of a multistage pump, the common passage can constitute the pressure passage of the forward pump unit and at the same time the suction passage of the rear pump unit. It is also possible for the common passage to connect the leakage-oil chambers of adjacent pump units.

Additionally, the use of a plurality of pump units on one shaft offers a possibility of counteracting the unilateral loading. Here, it is particularly advantageous to use three pump units arranged in parallel, the two outer units having half the capacity of the middle one and their curved tracks having a concentricity opposite to that of the middle pump unit. Consequently, the piston pressure of the middle pump counteracts that of the outer pumps; as a result, the bearing load is reduced to a minimum. In some cases it will suffice merely to establish a partial pressure balance, so that the two outer units 7 do not need to be exactly half the size of the middle unit.

In the case of reversible pumps, it is advantageous for the track carriers of all three pumps to be capable of being swung jointly for altering the capacity, but for the swing drives to be so coupled that the swinging movement of the outer pump units is in the opposite direction to that of the swinging movement of the middle pump unit. This means that the required pressure balance is maintained even when adjusting the pump capacity. A very precise pressure balance can be achieved by the use of an appropriate transmission system (e.g. by the correct choice of gear wheels, thread pitches etc.

On the other hand it often suffices, in the case of pump units operating on one system, merely to carry out regulation by swinging the track carrier. Here, it is best to regulate the larger pump units. In the case of multistage pumps however it may be expedient for the last stage to be regulable.

The diameter of the shaft does not need to vary very much even in the case where a plurality of pump units is involved. As a rule it suffices if the shaft, at the points thereof at which the piston carriers are secured, is at most 30 percent less than its maximum diameter. In particular, the greatest diameter can be at a point where a piston carrier is secured, the diameter being reduced towards the two ends. If three pump units are provided, the two outer ones thus have a somewhat smaller shaft diameter than the middle unit.

The invention also offers the possibility of building a large number of different kinds and sizes of pump using a series of common basic components rather in the manner of a building kit system. Here it is advantageous if the piston carriers, with the associated curved tracks and easing rings, as well as the remaining parts of the casing are of matching disc form such that at least two "discs" can also be used for another type of pump.

The invention will now be described in more detail by reference to two embodiments illustrated in the drawing, in which:

FIG. l is a longitudinal section through a pump comprising three pump units arranged in parallel,

FIG. 2 is a schematic illustration of the course of the passages in the pump of FIG. 1,

FIG. 3 is a section through the control arrangement, on the line A--A of FIG. 1,

FIG. 4 shows a cross section on the line B-B of FIG. ll,

FIG. 5 is a cross section, on the line CC, through an intermediate part of the casing for a modified construction comprising two pump units independent of each other, and

FIG. 6 is a section through the same casing part, seen in the direction of line D-D of FIG. ll.

The pump illustrated in FIGS. II to 4' has a casing which consists of a disclike cover plate I, a first casing ring 2, a first disclike intermediate part 3, a second casing ring 4, a second disclike intermediate part 5, a third casing ring 6 and a second disclike cover plate 7. The various parts are interconnected by screwbolts 8, sealing rings 9 being interposed. A shaft passes through the casing so assembled and is mounted in the casing parts ll, 3, 5 and 7 in bushes I1 and is additionally supported in a ball bearing unit 12.

The shaft 10 has three toothed portions, namely a middle portion 13 and two outer portions I4 and 15 for accommodating the piston carriers of three pump units a, b and c. Since these pump units are of the same construction, only unit c is provided with reference numerals in FIG. ll.

The piston carriers consist of two discs I6 and 17, each of which carries a series of pistons Itll, I9 in complementary cylinders. The inner end of each cylinder opens into an axial passage 20, which, at the junction, is surrounded by a pressure chamber 21, which is sealed by an O-ring 22. The pistons I8, 19 are caused by the centrifugal force to bear against the curved rack 23 of the track carrier 24, which can be swung about a journal 25. For the purpose of effecting the swinging movement, the track carrier has on'its opposite periphery a journal 26 which is flexibly held in a block 27, which can be swung by means of a screw in such a. manner that the curved track 23 can be swung out on both sides eccentrically on the central axis of the shaft I0. Contained in the surfaces defining the casing parts, here 5 and 7, are arcuate grooves 29 and 30, for the suction passage, and 31 and 32, for the pressure passage.

FIG. 2 illustrates schematically how the various pump units are interconnected. The cover plate I of the casing contains a suctionside port 33 and a pressure-side port 34. The casing parts 1-5 contain suction-side orifices 35, communicating with the port 33, and the casing parts ll-7 contain pressureside orifices 36 which constitute an extension of the port 34.

The suction-side grooves 30a, 29b, 30b and 290 communicate with the suction port 33 by way of passages 37 and 38 in the casing part 3 and passages 39 and 40 in the casing part 5. The grooves 290 and 30c are closed at one end. The pressure-side grooves 31a, 31b, 32b and 320 communicate with the pressure port 34 by way of the passage 41 in the-casing part 1, a passage 42 in the casing part 3, a passage 43 in the casing part and a passage 44 in the casing part 7. The grooves 32a and 32c are closed at one end. Consequently, the three pump units, a, b and c are arranged in parallel with each other. They aspirate the hydraulic fluid and pass it in the direction of the arrows. The pressure and suction sides of the pump units a and c can be interchanged for those of the pump unit b, this being achieved by the curved tracks 23 being of opposite eccentricity, so that very little loading of the shaft bearings occurs.

These conditions can be maintained even when the eccentricity is adjusted. A handwheel 45 is mounted on the threaded spindle 28b, with the help of which the block 27b can be axially displaced and the track carrier 24 can thus be swung. Mounted on the threaded spindle is a toothed wheel 46 which meshes with a toothed wheel 47 on the threaded spindle 28a and a toothed wheel 48 on the threaded spindle 28c. Consequently, when the handwheel 45 is turned, the blocks 27a and 270 are displaced in the opposite direction to that of block 27b. The thread on the spindles 28a and 28c is somewhat longer pitched than that on the threaded spindle 28b, since the radius of swing in the case of the pump unit b is greater than in the case of the units a and c. The entire displacement equipment is accommodated in a casing 49. Contained in the casing parts 1, 3, 5 and 7 are the leakage-oil passages 50, with which communicate all the leakage-oil chambers of the pump. A port for draining off the leakage-oil is contained at a point not illustrated.

With a few modifications, a completely different pump arrangement can be built-up from the components illustrated in FIG. 1. For example two pump units, independent of each other, can be driven by a correspondingly shorter shaft if the casing parts 5 and 7 and the pump unit c are replaced by a coverplate having a pressure port, and the pressure-side orifice in the casing part 2 is sealed. Then, although the hydraulic fluid is supplied through a common port 33, it is however passed through two pressure ports into systems that are independent of each other. In this arrangement is is of course advantageous if the two pump units can be adjusted independently of each other by dispensing with the coupling constituted by the toothed wheels 46 and 47, and actuating the threaded rod 28a by means of a separate handwheel.

A modified form of this construction, in which the casing part 3 is replaced by a casing part 51 for a pump arrangement comprising two pump units, is shown in FIGS. 5 and 6. The part 51 comprises a suction port 52 which projects radially outwards and which, by way of an axial passage 53, communicates with the suction side groove 54 of the pump unit b and the suction side groove 55 of the pump unit a. Also provided is a radial port 56 which communicates, by way of an axial connecting passage 57, with the pressure-side groove 58 of the pump unit b. The pressure-side passage 59 of the pump unit a is contained in the slightly modified coverplate l and communicates directly with an axially extending pressure port 60.

The pump unit 12 is adjusted with the help of the handwheel 45, and the pump unit a by means of an additionally provided handwheel 61.

lclaim:

l. A multistage radial piston pump assembly comprising casing means including end casing members having bearings, a shaft joumaled in said bearings, at least three spaced apart and cylindrically shaped piston carriers fixedly attached to said shaft, said piston carriers having radially disposed cylinders with pistons disposed in said cylinders, a track carrier surrounding each of said piston carriers, each of said piston carriers having distributing passages and at least one radially extending transfer surface having port means for said distribut- 7 ing passages, a casin part between each adjacent pair of said piston carners, eac said casing part having transfer walls abutting said transfer surfaces of said piston carriers, inlet and outlet passages in said casing means, said casing part having passages in fluid communication with said inlet and outlet passages, said casing part passages having fluid communication with said distributing passages of both of said piston carriers on opposite sides thereof, said casing part passages having at least three mouths in said transfer walls thereof, the middle one of said three piston carriers having approximately twice the capacity of each of the other two said carriers, said track carrier of said middle piston carrier being eccentrically disposed in the opposite direction from each of said track carriers of said outer piston carriers.

2. A multistage radial piston pump assembly according to claim 1 wherein said track carriers are pivotally mounted relative to said casing, regulating means for adjustingly pivoting said track carriers to alter their eccentricities relative to said piston carriers and thereby the respective capacities of said piston carriers, said regulating means being connected to said track carriers to pivot said middle track carrier in the opposite direction from the pivoting directions of said other two track carriers. 

1. A multistage radial piston pump assembly comprising casing means including end casing members having bearings, a shaft journaled in said bearings, at least three spaced apart and cylindrically shaped piston carriers fixedly attached to said shaft, said piston carriers having radially disposed cylinders with pistons disposed in said cylinders, a track carrier surrounding each of said piston carriers, each of said piston carriers having distributing passages and at least one radially extending transfer surface having port means for said distributing passages, a casing part between each adjacent pair of said piston carriers, each said casing part having transfer walls abutting said transfer surfaces of said piston carriers, inlet and outlet passages in said casing means, said casing part having passages in fluid communication with said inlet and outlet passages, said casing part passages having fluid communication with said distributing passages of both of said piston carriers on opposite sides thereof, said casing part passages having at least three mouths in said transfer walls thereof, the middle one of said three piston carriers having approximately twice the capacity of each of the other two said carriers, said track carrier of said middle piston carrier being eccentrically disposed in the opposite direction from each of said track carriers of said outer piston carriers.
 2. A multistage radial piston pump assembly according to claim 1 wherein said track carriers are pivotally mounted relative to said casing, regulating means for adjustingly pivoting said track carriers to alter their eccentricities relative to said piston carriers and thereby the respective capacities of said piston carriers, said regulating means being connected to said track carriers to pivot said middle track carrier in the opposite direction from the pivoting directions of said other two track carriers. 